1. Field of the Invention
This invention relates to a method of deformation measurement using speckle interferometry which enables nondestructive measurement of the deformation of a machine tool, industrial product or other such object using speckle interferometry.
2. Prior Art Statement
Since speckle interferometry can be used for contactless, highly accurate measurement of the vibration and deformation distribution of even rough surfaced objects such as machine components, it is an important measurement technology. Particularly significant one among the different types of speckle interferometry is electronic speckle pattern interferometry (ESPI). With ESPI it is possible to obtain interference fringes by taking a speckle pattern images with a TV camera and processing the video signals with electronic circuits or storing the images in a frame memory and processing them with a computer. Since ESPI is simpler to conduct than conventional real-time holography interferometry using photographic plates, it can be expected to find applications in nondestructive inspection etc. at the point of production.
On the other hand, even though such methods of measurement using interferometry are highly accurate, they have the disadvantage of being limited to a narrow measurement range. Speckle interferometry has a particularly severe limitation in that speckle noise on the interference fringes may, at large deformation or vibration, cause the density of the interference fringes to become so high as to make it impossible to read the interference fringes and thus impossible to carry out the measurement.
This invention was accomplished in light of the foregoing circumstances and has as its object to provide a method of deformation measurement using speckle interferometry which is able to maintain high measurement accuracy and achieve measurement over a wide range, specifically to enable measurement even when the deformation of the object being measured is on the millimeter order.